THE AORTA. 



541 



THE AORTA. 



The aorta (do/>ny, arteria magna) is the main trunk of a series of vessels which 

 convey the oxygenated blood to every part of the body for its nutrition. This 

 vessel commences at the upper part of the left ventricle, and, after ascending for 

 a short distance, arches backward to the left side, over the root of the left lung, 

 then descends within the thorax on the left side of the vertebral column, passes 

 through the aortic opening in the Diaphragm, and, entering the abdominal cavity, 

 terminates, considerably diminished in size, opposite the fourth lumbar vertebra, 



Right vagus. -X 

 Recurrent laryngeal. \ 



Left vagus. 

 Left phrenic. 

 Thoracic duct. 



Bight 

 coronary 



Left 

 oronary. 



FIG. 345. Plan of the 

 branches. 



FIG. 344. The arch of the aorta and its branches. 



where it divides into the right and left common iliac arteries. Hence its division 

 into the ascending aorta, the arch of the aorta or transverse aorta, and the 

 descending aorta, which last is again divided into thoracic aorta and abdominal 

 aorta, from the position of these part.<. 



THE ASCENDING AORTA. 



The ascending aorta is about two inches in length. It commences at the 

 upper part of the left ventricle, on a level with the lower border of the third costal 

 cartilage behind the left half of the sternum ; it passes obliquely upward, forward, 



